[Case of inferonasal subconjunctival orbital fat herniation]

We report a case with orbital fat herniation beneath the inferonasal conjunctiva, which is very rare in the literature.

A 52-year-old non-obese female. The subconjunctival mass in the right eye that had formed spontaneously at a young age was yellow, soft, and easily retreated into the orbit with pressure. A magnetic resonance image showed that the intraconal orbital fat herniated through a space that was formed by the inferonasal sclera and the intermuscular septum between the medial rectus muscle and the inferior rectus muscle. Surgical resection obtained good results.

This route of fat herniation in this case is similar to that of superotemporal lesions in previous reports. One possible explanation of the mechanism of such a rare lesion is congenital weakness in the inferonasal Tenon's capsule.